In vitro antibacterial activity of ceftizoxime against gram-negative strains

The in vitro activity of ceftizoxime against 200 clinical isolates of Enterobacteria and Pseudomonas, was compared with those of other beta-lactam antibiotics such as: cefotaxime, cefoperazone, cefuroxime, and the aminoglycosides gentamicin and amikacin. Ceftizoxime inhibited Escherichia coli and Klebsiella pneumoniae with doses from two to four fold lower than cefotaxime. Ceftizoxime and cefotaxime were more active than cefuroxime and cefoperazone against Enterobacter spp., and Proteus morganii. Ninety percent of the Serratia spp. were inhibited at 0.2 microgram/ml of ceftizoxime whereas the other cephalosporins needed doses up to thirty-two fold higher. The rest of the Proteus spp. were inhibited 90% with 0.8 or 3.2 micrograms/ml of ceftizoxime; on the contrary, to inhibit the same percentage of these bacteria, doses two to sixteen fold higher than cefotaxime or other cephalosporins were needed. Ceftizoxime was less active than amikacin against multiresistant Pseudomonas spp. Strains isolated from urine were generally more resistant to antibiotics than those encountered in other clinical material.